A coal-fired burner in a power plant receives pulverized coal in an air stream through one or more pipes sometimes called "burner lines". Control of the flow in these lines is needed to prevent burner line plugging, unbalanced coal flow, poor combustion in the burner, and excessive emissions. Existing orifices need to be changed from time to time to overcome many of these problems. What is needed is an on-line orifice which is capable of being adjusted to reduce burner line plugging and maintain a more balanced flow of coal, resulting in better combustion in the burner and lower emissions. The orifice should be capable of speedy adjustment without having to shut down the equipment.
In accordance with a specific embodiment of the invention about to be described, pulverized coal in an air stream is delivered to a coal burner by a pipe having a variable orifice comprising a plurality of flow restriction poles which project radially into the pipe. The poles lie in a common plane and are radially adjustable toward and away from each other to vary the amount of restriction to flow. Indicating means are provided to indicate the position of the poles. Preferably, the poles are easily removed when repair or replacement is necessary. Adjustment can be effected without interrupting the flow of coal in the pipe or otherwise shutting down the equipment.
One object of this invention is to provide an on-line variable orifice having the foregoing features and capabilities.
Another object is to provide an on-line variable orifice which is composed of a relatively few simple parts, is rugged and durable in use, is capable of easy adjustment without requiring the equipment to be shut down, and is capable of being inexpensively manufactured and assembled.
These and other objects, features and advantages of the invention will become more apparent as the following description proceeds, especially when considered with the accompanying drawings.